Laura Vera-Ramirez

Free radicals in breast carcinogenesis, breast cancer progression and cancer stem cells. Biological bases to develop oxidative-based therapies.

Oxidative stress leads to lipid, carbohydrate, protein and DNA damage in biological systems and affects cell structure and function. Breast cancer cells are subjected to a high level of oxidative stress, both intracellular and extracellular. To survive, cancer cells must acquire adaptive mechanisms that counteract the toxic effects of free radicals exposure. These mechanisms may involve the activation of redox-sensitive transcription factors, increased expression of antioxidant enzymes and antiapoptotic proteins. Moreover, recent data maintain that different breast cancer cell types, show different intracellular antioxidant capacities that may determine their ability to resist radio and chemotherapy. The resistant cell type has been shown to correspond with tumor initiating cells, also known as cancer stem cells (CSCs), which are thought to be responsible for tumor initiation and metastasis. Abrogation of the above-mentioned adaptive mechanisms by redox regulation in cancer cells opens a promising research line that could have significant therapeutic applications.

Hydroxytyrosol ameliorates oxidative stress and mitochondrial dysfunction in doxorubicin-induced cardiotoxicity in rats with breast cancer.

Oxidative stress is involved in several processes including cancer, aging and cardiovascular disease, and has been shown to potentiate the therapeutic effect of drugs such as doxorubicin. Doxorubicin causes significant cardiotoxicity characterized by marked increases in oxidative stress and mitochondrial dysfunction. Herein, we investigate whether doxorubicin-associated chronic cardiac toxicity can be ameliorated with the antioxidant hydroxytyrosol in rats with breast cancer. Thirty-six rats bearing breast tumors induced chemically were divided into 4 groups: control, hydroxytyrosol (0.5mg/kg, 5days/week), doxorubicin (1mg/kg/week), and doxorubicin plus hydroxytyrosol. Cardiac disturbances at the cellular and mitochondrial level, mitochondrial electron transport chain complexes I-IV and apoptosis-inducing factor, and oxidative stress markers have been analyzed. Hydroxytyrosol improved the cardiac disturbances enhanced by doxorubicin by significantly reducing the percentage of altered mitochondria and oxidative damage. These results suggest that hydroxytyrosol improve the mitochondrial electron transport chain. This study demonstrates that hydroxytyrosol protect rat heart damage provoked by doxorubicin decreasing oxidative damage and mitochondrial alterations.

Curcumin and liver disease.

Liver diseases pose a major medical problem worldwide and a wide variety of herbs have been studied for the management of liver‐related diseases. In this respect, curcumin has long been used in traditional medicine, and in recent years it has been the object of increasing research interest. In combating liver diseases, it seems clear that curcumin exerts a hypolipidic effect, which prevents the fatty acid accumulation in the hepatocytes that may result from metabolic imbalances, and which may cause nonalcoholic steatohepatitis. Another crucial protective activity of curcumin, not only in the context of chronic liver diseases but also regarding carcinogenesis and other age‐related processes, is its potent antioxidant activity, which affects multiple processes and signaling pathways. The effects of curcumin on NF‐κβ are crucial to our understanding of the potent hepatoprotective role of this herb‐derived micronutrient. Because curcumin is a micronutrient that is closely related to cellular redox balance, its properties and activity give rise to a series of molecular reactions that in every case and biological situation affect the mitochondria.

Hydroxytyrosol inhibits growth and cell proliferation and promotes high expression of sfrp4 in rat mammary tumours

SCOPE Hydroxytyrosol (a phenolic compound derived from virgin olive oil) has demonstrated an anti-tumour effect in several tumour cell lines in addition to other health-related properties. The aim of this study was to investigate, for the first time in an animal model of experimental mammary carcinoma, the anti-cancer ability of hydroxytyrosol and to discover which pathways are modified by hydroxytyrosol. METHODS AND RESULTS Dimethylbenz[α]anthracene-induced mammary tumours were induced in 28 female Sprague-Dawley rats and ten of them were treated with hydroxytyrosol (0.5 mg/kg b.w. 5 days/week for 6 wk). cDNA microarray and quantitative RT-PCR experiments were performed. Hydroxytyrosol was found to inhibit the experimental mammary tumour growth and proliferation rate, with results comparable to those of doxorubicin but better with regard to the histopathological outcome. It also altered the expression of genes related to apoptosis, cell cycle, proliferation, differentiation, survival and transformation pathways. CONCLUSIONS This study shows that hydroxytyrosol exerts anti-cancer effects in Sprague-Dawley rats with experimental mammary tumours, inhibiting growth and cell proliferation in mammary tumours. Moreover, hydroxytyrosol alters several genes associated with cell proliferation, apoptosis and the Wnt signalling pathway, promoting a high expression of Sfrp4. However, further studies are necessary to better understand the mechanisms of hydroxytyrosol.

Gene-expression profiles, tumor microenvironment, and cancer stem cells in breast cancer: Latest advances towards an integrated approach

During the past decade, several high throughput analytical methods for gene-expression profiling have been developed. DNA microarrays and multiplex RT-PCR have been applied in the field of breast-cancer research to establish new molecular taxonomic classifications, or a selected group of genes able to predict the prognosis of the patients and/or their response to chemotherapy. This technology provides an opportunity to refine the anti-neoplastic treatment and avoid the currently observed under- and over-treatment of breast-cancer patients. In parallel, high throughput technologies for gene-expression analysis have been applied to research on cancer stem cells (CSCs) and the tumor microenvironment, offering a wider vision of the molecular processes that influence carcinogenic events, disease development, and the response to the treatment of breast-cancer patients. In this report, we briefly revisit the most relevant genomic studies on breast-cancer prognosis and prediction to introduce the latest advances in tumor dormancy, its implications in the clinical outcome of disease-free patients and its connection with CSCs biology and microenvironment influence in the metastatic process. Finally, we have discussed the contribution of the results of these studies to the design of new experimental strategies oriented towards personalized medicine.

Impact of Diet on Breast Cancer Risk: A Review of Experimental and Observational Studies

Breast cancer, which presents the highest global incidence of all female cancers, is caused by the interaction of genetic and environmental factors. Among the latter, diet has attracted considerable attention, as it is a modifiable risk factor and thus offers an opportunity to design preventive strategies. Nevertheless, only alcohol consumption has been unequivocally related to increased breast cancer risk. Despite the failure of observational studies in human populations to clearly define the nature of the relationship between specific nutrient exposures and breast cancer risk, in vivo and in vitro studies strongly suggest its existence. Moreover, studies at the molecular level have identified the putative action mechanism by which the nutritional constituents of specific foodstuffs may exert protective or enhancing effects with respect to breast cancer risk. The inadequate experimental design of some observational studies, or the occurrence of measurement errors and/or recall bias during data collection, or insufficient follow-up and subject characterization, may underlie these controversies. By improving the methods used to study the relationship between diet and breast cancer risk, and by applying new technologies linked to novel approaches such as “nutrigenomics,” it might be possible to derive effective recommendations for breast cancer prevention and thus improve anti-cancer treatment.

Long-term effects of systemic cancer treatment on DNA oxidative damage: The potential for targeted therapies

The main pathological consequence of free radical exposure is DNA damage, which is known to induce cell transformation and to facilitate important mutations in cancer progression. It is a matter of intense discussion whether the drug-induced production of free radicals limits the therapeutic efficacy of chemotherapeutics and enhances their toxicity or whether they may be enhanced to provoke cancer cell apoptosis. This paper reviews essential molecular processes to better understand the controversial role of free radicals in cancer development and progression, and discusses some novel therapeutic strategies based on oxidative stress induction and prevention.

Does Chemotherapy-Induced Oxidative Stress Improve the Survival Rates of Breast Cancer Patients?

Antineoplastic agents induce oxidative stress leading to lipid, carbohydrate, protein, and DNA damage. We sought to explore the role of drug-induced oxidative stress on breast cancer patients survival. We observed that neoadjuvant patients presented a marked raise in DNA damage and protein carbonyl levels after chemotherapy, whereas postchemotherapy DNA repair activity of the KU86 enzyme and total antioxidant capacity of the plasma were higher in the adjuvant group. With respect to patients survival, we observed that increasing levels of KU86 and antioxidant capacity of the plasma during chemotherapy significantly influenced the survival rates of the patients, protecting from disease recurrence and death. Our results suggest that chemotherapy induces a certain level of systemic oxidative stress, which is maintained along successive clinical interventions and could influence the clinical outcome of the patients.

Transcriptional shift identifies a set of genes driving breast cancer chemoresistance.

Background Distant recurrences after antineoplastic treatment remain a serious problem for breast cancer clinical management, which threats patients’ life. Systemic therapy is administered to eradicate cancer cells from the organism, both at the site of the primary tumor and at any other potential location. Despite this intervention, a significant proportion of breast cancer patients relapse even many years after their primary tumor has been successfully treated according to current clinical standards, evidencing the existence of a chemoresistant cell subpopulation originating from the primary tumor. Methods/Findings To identify key molecules and signaling pathways which drive breast cancer chemoresistance we performed gene expression analysis before and after anthracycline and taxane-based chemotherapy and compared the results between different histopathological response groups (good-, mid- and bad-response), established according to the Miller & Payne grading system. Two cohorts of 33 and 73 breast cancer patients receiving neoadjuvant chemotherapy were recruited for whole-genome expression analysis and validation assay, respectively. Identified genes were subjected to a bioinformatic analysis in order to ascertain the molecular function of the proteins they encode and the signaling in which they participate. High throughput technologies identified 65 gene sequences which were over-expressed in all groups (P ≤ 0·05 Bonferroni test). Notably we found that, after chemotherapy, a significant proportion of these genes were over-expressed in the good responders group, making their tumors indistinguishable from those of the bad responders in their expression profile (P ≤ 0.05 Benjamini-Hochgerg`s method). Conclusions These data identify a set of key molecular pathways selectively up-regulated in post-chemotherapy cancer cells, which may become appropriate targets for the development of future directed therapies against breast cancer.

Oxidative stress status in metastatic breast cancer patients receiving palliative chemotherapy and its impact on survival rates

Antineoplastic agents are known to induce the production of free radicals leading to cell damage. These adverse effects may fuel the acquisition of new mutations and the development of treatment resistances. We selected 30 metastatic breast cancer patients receiving palliative chemotherapy, and paired blood samples, before and after chemotherapy, were extracted. We analysed DNA, lipid and protein oxidative damage markers and determined the extent of antioxidant and repair defences activation at the systemic level. We found that the DNA repair activity of the KU86 enzyme was significantly lower after chemotherapy and the antioxidant capacity of the plasma was significantly higher after treatment. Cox regression analysis revealed a significant effect of KU86 activity on the survival rates of those patients who received anthracyclines as part of their treatment. The high clinical heterogeneity of metastatic breast cancer patients warrants further studies to clarify the role of DNA repair and systemic antioxidant capacities during chemotherapy.